1. Field of the Invention.
The present invention relates to a process for producing a protein product using a resonating chamber.
2. Description of the Prior Art.
Prior art processes have lowered the pH of protein solutions in a variety of ways to try to produce a suitable curd. For example, the manufacture of cheese cultures of acid-forming bacteria are frequently used, either separately or in conjunction with coagulating enzymes and/or heat to produce the desired type of curd. An alternative to using acid forming bacteria to form acid cheeses such as Cottage, Cream, and Baker's cheese is to directly acidify the milk. However, the direct acidification of milk has always been limited by the problem of localized precipitation or coagulation of the protein, which produces an unusable product.
An example of one approach that has been used to avoid the localized coagulation problem is to directly acidify cold milk with food grade acid until the milk pH is just above a critical point where further acid addition will cause coagulation, usually about pH 5.2 in milk. Then an acidogen is uniformally dispersed throughout the milk, and the milk allowed to stand in a quiescent state until the acidogen lowers the milk pH to the isoelectric point of casein, the major milk protein, to produce a curd. The Hammond U.S. Pat. No. 2,982,654 describes the use of what is now a well known acidogen, glucono-delta-lactone. The Corbin, Jr. U.S. Pat. No. 3,340,066, although making a buttermilk product, also adds acid directly to the milk, lowering the pH to a range between about 4.8 to 5.1 and then permitting the acidogen to lower the pH of the milk to about 4.2 to about 4.5. Other processes using an acidogen to lower the pH below the coagulation point of the milk include the Corbin, Jr. U.S. Pat. No. 4,066,791, the Metz U.S. Pat. No. 4,264,636, the Pearline et al U.S. Pat. No. 4,352,826, and the Loter U.S. Pat. No. 4,374,152.
Another process similar to the process of adding acidogen is the process of directly adding acid to cold milk until the Ph is reduced to approximately 5.2, and then adding an acid-producing enzyme which lowers the pH to the isoelectric point. The Foster, Jr. et al U.S. Pat. No. 3,172,767, the Little U.S. Pat. No. 3,406,076, the Corbin, Jr. U.S. Pat. No. 3,620,768 and the Loter et al U.S. Pat. No. 3,882,250 disclose variations of such a process for the production of cheese curd.
Still another method used in the production of cheese curd includes the direct acidification of the milk after the milk has been cooled to a temperature where coagulation will not occur. The milk is then heated whereupon the coagulation occurs. One such process is disclosed in the Ernstrom U.S. Pat. No. 3,298,836. Another variation of cooling, acidifying and then heating the milk is discussed in the British Patent to Battelle Development Corporation 1,247,415. In the British Battelle Patent, a proteolytic enzyme is also added to effect coagulation.
The Little U.S. Pat. No. 3,792,171 describes a process wherein solid acid particles are treated with a coating that will disperse or dissolve in the milk at a rate that delays the dissolution of the acid particles and effects relatively slow and uniform acidification.
The Little U.S. Pat. No. 3,359,116, although describing a process for the making of a sour cream-type product or cream cheese, adds acid to a milk that has been stabilized using a vegetable gum or gelatin.
In another Little U.S. Pat. No. 3,953,610 a process is disclosed for the direct acidification of milk wherein the milk is mixed at a high velocity by a propeller-type agitator. Acid is sprayed on the milk at a location of high velocity.
The Goujard U.S. Pat. No. 3,845,226 discloses a process that produces a very fine, non-granular curd. The process acidifies milk by mixing with the milk an acidifed serum that includes whey that has been acidified to a pH range of between 0.5 to 2.5 by electrodialysis. A sufficient amount of the serum is added to lower the pH of the milk below the isoelectric point of casein. The serum and the milk are mixed in a mixer.
In the recent Lundstedt et al U.S. Pat. No. 4,416,905, a method is described for the production of cultured dairy products, such as buttermilk, yogurt or sour cream. The milk is fermented using a bacterial fermentation culture. The fermentation of the medium is allowed to proceed for sufficient time to achieve a pH in the range of 6.0 to about 4.9 at which time the milk is cooled to reduce the fermentation rate. Then the pH is lowered to 4.7 or less using food grade acids.